In general, gradient formers are used to mix two fluids together in either a linear or an exponential fashion. To make perfect linear gradients, the geometry of the two chambers must be identical and the fluid level must drop at the same rate in each chamber. During operation, the fluid flows from the reservoir chamber into the mixing chamber. The concentration of the stream of gradient exiting from the mixing chamber changes at a constant rate with respect to volume. The result is a perfectly linear gradient varying between two original limits. The gradient slope can be either positive or negative, depending upon the relative concentrations initially placed in the two chambers. Linear gradient formers are used in centrifugation, electrophoresis and liquid chromatography.
Prior art linear gradient formers of the dual chamber type are not capable of controlling the rate at which the fluid drops in each chamber; therefore, the gradients that are formed are not accurate. A prior art linear gradient former may work for fluids of one specific set of physical properties for which it was designed. However, prior art gradient formers are unable to compensate for fluids of different viscosity because their cylinders are open to the atmosphere. One typical use of linear gradient formers are used in centrifugation to create sucrose gradients in centrifuge rotor tubes or for continuous flow zonal rotors. Biological samples are separated via density gradient centrifugation. Accuracy of the density gradient is extremely important to obtaining a desired separation.
Gradient formers are also used to create the cast gels in electrophoresis applications.
In gravity flow column liquid chromatography, the gradient former is used for separation of pressure sensitive biological samples. The gradient former can also be used as a pre-pump gradient former for high performance, high pressure liquid chromatography.
Prior art linear gradient formers, which are used to fill centrifuge tubes, are inaccurate because their cylinders are open to the atmosphere and they cannot compensate for different fluids of different viscosities; therefore, the mixing is very inaccurate. These gradient formers are often used to fill centrifuge tubes. Typically, prior art gradient formers fill one tube at a time. Using a small syringe, the operator must manually refill the gradient former for each centrifuge tube. This is a slow, tedious, labor-intensive process, and the resulting gradients formed are inaccurate. Therefore, it is a principal object of the present invention to provide a gradient former which is capable of controlling the fluid level in each chamber regardless of the density or viscosity of the particular fluid.
Another object of the present invention is to provide a gradient former having the characteristic features described above which is capable of providing accurate linear gradients for all fluids regardless of the physical properties of the particular fluids being employed.
Another object of the present invention is to provide a linear gradient having the characteristic features described above which is capable of providing the operator with complete control over the fluid flow rate, and the resulting fluid level drop in each chamber.
A further object of the present invention is to provide a gradient former having the characteristic features described above which also provides for a quick and easy filling of the fluid chambers regardless of the volume to be filled.
Another object of the present invention is to provide a gradient former having the characteristic features described above which is capable of providing accurate linear gradients quickly and easily with equal efficacy regardless of the volumes required by the user.
Other and more specific objects will in part be obvious and will in part appear hereinafter.